Networks enable computers and other devices to communicate. For example, networks can carry data representing video, audio, e-mail, and so forth. Typically, data sent across a network is divided into smaller messages known as packets. By analogy, a packet is much like an envelope you drop in a mailbox. A packet typically includes “payload” and a “header”. The packet's “payload” is analogous to the letter inside the envelope. The packet's “header” is much like the information written on the envelope itself. The header can include information to help network devices handle the packet appropriately. For example, the header can include an address that identifies the packet's destination.
A series of related packets can form a connection. A connection is often identified by a combination of different portions of a packet known as a tuple. For example, a tuple is commonly formed by a combination of source and destination information of a packet header.
A variety of networking protocols maintain state information for a connection. For example, the Transmission Control Protocol (TCP) stores state data for a connection in a Transmission Control Block (TCB). A TCB includes state data such as the last received byte, the last successfully transmitted byte, and so forth. Typically, connection state data is accessed and, potentially, updated for each packet in a connection. In a multi-processor system, this can create contention issues between processors handling packets for the same connection. That is, for example, different processors handling data for the same connection may each attempt to access a connection's state data at the same time, creating requirements for data locking and introducing delay as the processors wait for access to the connection state data.
Contention between the processors, however, can be reduced by mapping respective connections to the respective processors. For example, a network interface controller (NIC) may perform a hash on a tuple of a received packet and use the hash to determine a processor to handle a given packet. Directing packets in a flow to the same processor can help pin down state information. This can enable the processor to retain the state data for a connection in local processor memory (e.g., cache memory) and reduce contention between processors trying to access the same connection state data.